1. Field of the Invention
This invention relates to a camera zoom lens automatic magnification changing device for automatically adjusting the focal distance of a zoom lens in accordance with the distance of the subject, the size of the subject within the angle of view, etc., such a device being adapted for use in a still camera, a movie camera or the like.
2. Background Art
Conventionally, as disclosed in Japanese Laid-Open (Kokai) Patent Application No. 232315/89, there has been proposed a device in which the distance of the subject at each of at least three points of the subject within the angle of photographing view is measured to judge the size of the subject within the angle of photographing view, and in accordance with the distance of the subject, the size and position of the subject, the magnification of the lens is changed to the optimum zoom ratio. In such a device, even if the size of the subject differs, the size of the subject within the angle of view can be kept constant to a certain degree, and even if the subject is positioned out of the center of the angle of view, the distance can be accurately measured. Thus, such a device has a feature that the magnification-changing control, etc., are not affected.
However, when actually photographing, there are also many factors other than the size of the subject, and it is desirable that in view of such factors, the lens be changed in magnification to obtain an optimum condition. For example, when photographing outdoor scenery, or a person with scenery used as a background, it is preferred that the zoom ratio be set to the wide-angle side from the original zoom ratio determined by the distance of the subject and the size of the subject. In contrast, when photographing a sport scene, it is preferred that the zoom ratio be set to the telephotographic side from the original zoom ratio.
Thus, despite the size and the position of the subject, the required zoom ratio varies in accordance with the photographing situation. Therefore, if, in accordance with the photographing conditions, a more proper magnification-changing program is automatically selected, advantageous control of photography is achieved.